This invention relates to a novel photocurable composition containing a silicon compound. More particularly, it relates to a photocurable silicone composition which may liberate a silanol compound by irradiation with light, particularly with an ultraviolet ray, to undergo polymerization of the silanol compound, optionally in the presence of a silanol-condensing catalyst.
As photocurable silicon compound compositions, there has been known a composition having for its component an organopolysiloxane having a silicon atom to which a vinyl group or a group of methacrylate or acrylate is directly bonded (as disclosed, for example, in the specifications of Japanese Unexamined Patent Publication No. 120619/1980, Japanese Unexamined Patent Publication No. 125123/1980, Unexamined Patent Publication No. 137129/1980, U.S. Pat. 3,726,710; U.S. Pat. No. 3,873,499 and U.S. Pat. No. 4,064,017).
However, since the organopolysiloxane used therein is poor in the photocuring reactivity, it has been used generally in combination with a photosensitizer such as benzophenone, aetophenone or benzoinether. As a result, the composition containing such a sensitizer has an advantage that the curing reaction occurs even by irradiation with light of relatively longer wavelength, which advantage, however, results all from the photosensitizer and not from the organopolysiloxane itself. Moreover, the resultant cured product is disadvantageous in that it is poor in heat-stability.